1. Technical Field
The technical field relates to a non-volatile memory, and more particularly, to a non-volatile memory apparatus and an empty page detection method thereof.
2. Description of Related Art
Comparing to a traditional hard drive disk (HDD) apparatus, a solid state drive (SSD) with a flash memory having characters such as fast read/write and low power consumption. The SSD is a usual data storage apparatus. During the operating procedure of the SSD, the system (firmware and hardware) of the SSD needs to maintain lots of updated management information, such as addresses mapping information, flash memory condition information and others. The said flash memory condition information includes programing/erasing count, valid page count and other condition information. The said updated management information would be disappeared with the unexpected power-off event. When the power supply is recovered, the system of the SSD needs to recover a state which is before the unexpected power-off event (e.g., the updated management information). Wherein, the system of the SSD needs to determine which memory page(s) has been written, or which memory page(s) has not been written (e.g., an empty page).
For some of the types of flash memory products, the logical value of every bit of erased memory cells is “1”. Therefore, (the logical bit value of) all the bits of an erased memory page (i.e., a memory page having no data, or an empty page) should be “1”. In general, the common empty page detection method would be counting an amount of bits being “1” in a content of one target memory page. And, if all bits in the content of the target memory page are “1”, it is indicating that the target memory page is an empty page.
For other of the types of flash memory products, a scrambler is deposed in the flash memory apparatus. With the operation of the scrambler, the contents of memory pages are approximate random. Therefore, not all the bits of an empty page would be “1”. And, clearly the foregoing common empty page detection method would not be suitable for the flash memory apparatus having the scrambler since the method cannot correctly determine whether the target memory page is an empty page according to the read content of the target memory page.